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Expression Analysis of Cytoskeletal and Ribosomal Genes during Adult Diapause in the Northern House Mosquito, Culex pipiens

Kim, Mijung
http://rave.ohiolink.edu/etdc/view?acc_num=osu1250174898

Abstract Details

2009, Doctor of Philosophy, Ohio State University, Entomology.
The northern house mosquito Culex pipiens L., a vector of arthropod-borne viruses, is capable of entering an overwintering dormancy known as diapause. Adult diapause in C. pipiens is regulated at environmental, hormonal, and molecular levels. In this thesis, select gene groups including cytoskeletal genes and genes encoding ribosomal proteins (rps) were cloned and their expression patterns and function related to diapause were examined. The gene in C. pipiens that encodes beta-tubulin, a major cytoskeletal gene, has high similarity with beta-tubulins from other insects. This gene was up-regulated in thoracic muscles (mostly flight muscles) of nondiapausing female mosquitoes but was down-regulated during diapause. Similarly, microtubule abundance was significantly lower in thoracic muscles of diapausing females than in thoracic muscles from nondiapausing females. Microtubule abundance also declined in midguts of nondiapausing females after low temperature exposure. However, in diapausing females, microtubule abundance was already low and remained at a low level even after low temperature exposure. These results showing lower expression of beta-tubulin and microtubule abundance in the thoracic muscles suggest a link to the reduced flight activity during diapause and in response to low temperature. Two ribosomal proteins located on a small ribosomal subunits, rpS3a and rpS2, are proposed to function in suppressing ovarian development during adult diapause in C. pipiens based on RNA interference (RNAi) results. RpS3a was continuously expressed in nondiapausing females but was less expressed for a brief period 7-10 days after adult eclosion in diapausing females. When RNAi was directed against rpS3a in nondiapausing females ovarian development was halted as it is in diapause. The effect persisted for approximately 10 days. Application of juvenile hormone III, an endocrine trigger known to terminate diapause, rescued the arrested ovarian development caused by dsrpS3a injection. RpS2 also has a potential role in regulating reproductive diapause in C. pipiens. RpS2 is expressed strongly from 1 day to 1 month in nondiapausing females, whereas it is down-regulated on day 5-18 in diapausing females. RNAi directed against rpS2 suppressed the growth of follicles in nondiapausing female mosquitoes, and topical JHIII application again was able to rescue the arrested follicles. RpL19 was used as a control ribosomal protein, and the injected RNAi directed against rpL19 did not affect the arrest of ovarian development. Thus, the results suggest that rpS3a and rpS2 are ribosomal proteins that play a role in regulating the ovarian development related to diapause in this species. Another ribosomal protein, rpS6, was examined in relationship to heat shock protein 90 (hsp90) in nondiapausing and diapausing female mosquitoes. Both rpS6 and hsp90 were continuously expressed in nondiapausing females, but they were synchronously down-regulated around day 14 after adult eclosion in diapausing females. RNAi directed against hsp90 was performed to evaluate a possible correlation with rpS6. When RNAi was directed against hsp90 in nondiapausing females, rpS6, as well as hsp90, was suppressed. These results suggest that the down-regulation of hsp90 in diapausing mosquitoes contributes to the low expression of rpS6 during diapause.
David Denlinger (Advisor)
Susan Fisher (Committee Member)
Glen Needham (Committee Member)
Peter Reiser (Committee Member)
132 p.
Entomology
diapause; culex pipiens; low temperature; cytoskeletal gene; ribosomal protein

Recommended Citations

Citations

  • Kim, M. (2009). Expression Analysis of Cytoskeletal and Ribosomal Genes during Adult Diapause in the Northern House Mosquito, Culex pipiens [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1250174898

    APA Style (7th edition)

  • Kim, Mijung. Expression Analysis of Cytoskeletal and Ribosomal Genes during Adult Diapause in the Northern House Mosquito, Culex pipiens. 2009. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1250174898.

    MLA Style (8th edition)

  • Kim, Mijung. "Expression Analysis of Cytoskeletal and Ribosomal Genes during Adult Diapause in the Northern House Mosquito, Culex pipiens." Doctoral dissertation, Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1250174898

    Chicago Manual of Style (17th edition)

osu1250174898
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© 2009, all rights reserved.
This open access ETD is published by The Ohio State University and OhioLINK.